Insert for paper machine drainage elements

ABSTRACT

A replaceable drainage element having a wear resistant insert composed of a plurality of discrete elements arranged in end-toend relationship and secured to a supporting plate which is removably secured in a groove in the supporting surface of the drainage element.

United States Patent 91 Beacom et al.

[ INSERT FOR PAPER MACHINE DRAINAGE ELEMENTS [76] Inventors: Oliver J. Beacom, 141 Arrowhead Cresent, Pointe Claire, Quebec; Donald G. MacBean, 13241 Aragon St., Pierrefonds, Quebec, both of Canada Notice: The portion of the term of this patent subsequent to May 8, 1990. has been disclaimed.

[22] Filed: Jan. 22, 1973 [21] Appl. N0.: 325,079

Related US. Application Data [63] Continuation-impart of Ser. No. 118,767, Feb. 25,

1971, Pat. N0. 3,732,142.

[30] Foreign Application Priority Data Mar. 10, 1970 Canada 077028 1*May 20, 1975 [52] US. Cl 162/374; 162/352 [51] Int. Cl D2lg 9/00 [58] Field of Search 162/352, 374

[56] References Cited UNITED STATES PATENTS 3,393,124 7/1968 Klinger et al. 162/352 3,446,702 5/1969 Buchanan 162/374 3,732,142 5/1973 Beacom et al. 162/374 Primary Examiner-S. Leon Bashore Assistant Examiner-Alfred D'Andrea, Jr.

[5 7 ABSTRACT A replaceable drainage element having a wear resistant insert composed of a plurality of discrete elements arranged in end-to-end relationship and secured to a supporting plate which is removably secured in a groove in the supporting surface of the drainage element.

7 Claims, 2 Drawing Figures INSERT FOR PAPER MACHINE DRAINAGE ELEMENTS CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of US. patent application Ser. No. 118,767, filed Feb. 25, 1971 now US. Pat. No. 3,732,142. 1

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to drainage elements for paper making machines. More particularly, the present invention relates to wear resistant inserts for replaceable drainage elements for use on paper machines.

2. Description of Prior Art Replaceable drainage elements such as foils for paper machines have gained acceptance in the trade and are being widely used. One such drainage element is shown in Canadian Pat. No. 717,289 issued Sept. 7, 1965 to Johnson Wire Works Limited. These replaceable drainage elements are normally made of a synthetic plastic such as high molecular weight, high density polyethylene which is a very inert material but is subject to wear. To reduce the wear problems, it has been proposed to provide wear resistant inserts at appropriate locations on the surface of the drainage element.

It has been proposed to make these wear resistant inserts by several means. One is to form the insert of a wear resistant material such as tungsten or silicon carbide and apply this directly to the drainage element. It has also been proposed to use a plurality of discrete elements in abutting relationship. It is with this latter type of inserts that the present application is primarily concerned.

With discrete abrasion resistant elements used in abutting relationship to form the insert, difficulties have been encountered with the elements not remaining in their proper positions. This problem is aggravated due to the difference in expansion coefficients between the body of the drainage element and the inserts themselves. The inserts generally have an extremely low coefficient of expansion whereas the polyethylene body of the drainage element has a coefficient of expansion in the range of 120 X The paper machine operates at temperatures ranging from about 70 to 120F. and, therefore, the difference in expansion between the insert and the body of the foil in a relatively wide machine is appreciable. It will be appreciated that even a very slight spacing between adjacent insert elements results in poor formation and defects in the resultant paper product. For this reason, inserts formed from a plurality of discrete elements have not gained acceptance.

Furthermore, the inserts used, particularly when formed completely of silicon carbide or the like, are relatively brittle and do not have the flexibility of the remainder of the drainage element. It is believed that this rigidity results in damage by chipping of the edges of the inserts when handling the drainage elements.

SUMMARY OF INVENTION It is thus an object of the present invention to provide an improved insert specifically adapted for use with replaceable drainage elements.

Accordingly, from a broad aspect, the present invention provides a replaceable drainage element for a paper machine and having an elongated body formed with a supporting surface and a diverging surface. An insert receiving groove is provided in the supporting surface and extends longitudinally of the body and defines an undercut portion extending longitudinally in each side wall thereof. A wear resistant insert is removably retained within the groove and is unaffected by the differential in expansion between the body and the wear resistant insert at the operating temperature of the paper machine.

BRIEF DESCRIPTION OF DRAWINGS Further features, objects and advantages of the present invention will be evident from the following detailed description of a preferred embodiment of the present invention when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a partial perspective view of a replaceable drainage foil having a wear resistant insert constructed according to the present invention incorporated therein; and

FIG. 2 is a perspective view of an insert constructed in accordance with the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, the foil includes a main foil body 10 which is adapted to be mounted on a fourdrinier paper machine in a manner such that the wire of the machine (not shown) travels over the element 10 in the direction of the arrow 11.

The drainage element 10 includes a body member 12 formed of suitable material such as high density, high molecular weight polyethylene and having a leading edge 14, a supporting surface 16, and a diverging surface 18. This foiling element is positioned under the wire of a paper machine in a manner such that the wire travels over the foil moving in the direction of the arrow 11 shown in FIG. 1. The surface 16 serves as a supporting area for the wire while the surface 18 causes suction to be applied to the wire.

An insert receiving groove 20 is formed in the body 12 of the element so that it extends longitudinally of the foil and opens in the supporting area 16. At least the upper portion of this groove is provided with an undercut section 22 adapted to receive the corresponding angulated longitudinal edges of an insert 24. Below the undercut section 22 ,is a channel 26 in which a supporting plate 30, to be described later, is received.

The wear resistant insert 24 is formed from a plurality of discrete wear resistant elements 30 each of which is provided with a beveled edge 28 adapted to be received in the undercut section 22 of the groove 20 so that the individual elements 30 may be slid axially into position. These discrete elements 30 of the insert 24 will be described indetail hereinbelow.

As can be seen from FIG. 2, insert 24 is made from a plurality of discrete elements 30 mounted on a supporting plate 31. These discrete elements 30 are each formed of wear resistant material such as tungsten or silicon carbide and define an upper wear resistant surface 29, beveled edges 28 and flat abutting end faces 27. At the bottom side of the abutting ends of each element 30 there is formed a chamfer 33. The elements 30 are glued to a backing plate 31, which, like the wear resistant element 30 has a lower coefficient of thermal expansion than the material of the body member, and are held in this position. The insert element 24 may be produced by stressing the plate 31 when the element 30 is positioned thereon and the glue'isa'pp'lied' and set so that when the tension is released, the discrete elements will be held tightly together. The degree of stressing applied to the plate 31 will be sufficient to hold the elements 30 in clamped position after the stressing forces are released under the temperature conditions encountered on the paper machine.

Preferably there will also be glue between the chamfered edges at the bottom of the abutting faces in the joint 32 of adjacent elements 30, however, the adjacent edges of the upper abrasive resistant surface of the elements will usually be in intimate abutting relationship.

An alternate mode of construction would be to compress the element 30 together and glue them in this compressed state to the backing plate 31.

Stressing of the backing plate 31 can also be attained by heating so that the backing plate 31 is at a higher temperature than the elements when the elements 30 are glued thereon in abutting relationship.

If the backing plate 31 has substantially the same coefficient of expansion as the elements 30, then the requirement for prestressing, of course, is no longer necessary. However, generally this backing plate 31 will be prestressed.

Preferably, the glue used to attach the wear resistant elements 30 will be of a waterproof, flexible type that does not harden or dry out to the extent that it becomes brittle. We recommend the use of flexible contact cement identified by the trade mark Pliobond or one of the silicone rubber adhesives that vulcanize at room temperature. Such adhesives act to absorb the stress of small differentials in expansion that occur between the wear resistant elements and the backing plate and also act as a cushion to absorb stress which might otherwise cause chipping or fracture of the brittle wear resistant elements during handling of the insert element 24.

The insert element 24 is slid axially into the groove whereby the angulated edges 28 of the elements are received within the under portion 22 and the backing plate 31 in the channel 26. The insert element 24 will be retained securely in the groove 20 and remains unaffected by the differential in the expansion between the insert and the foil body as described earlier.

Each of the elements 30 have a length L of less than 6 inches and preferably will be about 2 inches long (see FIG. 2). The width W will generally be less than threeeighths of an inch and preferably about one-fourth of an inch and the thickness T of each element will be in the order of less than 0.15 inches. With a one-fourth inch width element the thickness preferably will be about 0.125 inches.

We claim 1. A replaceable drainage element for paper machines, said drainage element having an elongated body formed with a supporting surface and a diverging surface, an insert receiving groove in said supporting surface longitudinally of said body and located a short distance behind a leading edge of said body, said insert receiving groove having opposed side walls the upper portion of which defines an undercut section terminating in a channel section in the base of said groove, a wear resistant insert removably retained securely within said groove and unaffected by the differential in expansion between said body and said wear resistant insert at operating temperatures of said paper machine, said insert being formed of a plurality of discrete elongated elements glued to a backing plate and maintained in end abutting relationship.

2. A drainage element as claimed in claim 1 wherein said wear resistant insert comprises a plurality of discrete elongated elements each having a wear resistant upper surface, flat end faces and beveled side edges; said elements being secured in end abutting relationship to a backing plate.

3. A drainage element as claimed in claim 2 wherein said discrete elongated elements have a chamfered portion on their lower end faces and are glued to said backing plate while said elements are compressed in said end abutting relationship and glued onto said backing plate.

4. A drainage element as claimed in claim 2 wherein said discrete elongated elements are compressed and glued together at their end faces and also glued to said backing plate with said plate in a stressed state.

5. A drainage element as claimed in claim 2 wherein said backing plate is expanded by heat at a higher temperature than said insert elements, said elements being glued to said expanded backing plate in intimate end abutting relationship with each other so that when the temperature of said backing plate is lowered the backing plate contracts applying compression stress to the elements in end abutment.

6. An element as claimed in claim 2 wherein said undercut portion extends in the upper portion of said side wall, said beveled side edges of said elements being retained in said upper portion of said groove with said backing plate thereunder.

7. An element as claimed in claim 1 wherein said wear resistant insert has a lower coefficient of thermal expansion than the coefficient of thermal expansion of said body. 

1. A REPLACEABLE DRAINAGE ELEMENT FOR PAPER MACHINES, SAID DRAINAGE ELEMENT HAVING AN ELONGATED BODY FORMED WITH A SUPPORTING SURFACE AND A DIVERGING SURFACE, AN INSERT RECEIVING GROOVE IN SAID SUPPORTING SURFACE LONGITUDINALLY OF SAID BODY AND LOCATED A SHORT DISTANCE BEHIND A LEADING EDGE OF SAID BODY, SAID INSERT RECEIVING GROOVE HAVING OPPOSED SIDE WALLS THE UPPER PORTION OF WHICH DEFINES AN UNDERCUT SECTION TERMINATING IN A CHANNEL SECTION IN THE BASE OF SAID GROOVE, A WEAR RESISTANT INSERT REMOVABLY RETAINED SECURELY WITHIN SAID GROOVE AND UNAFFECTED BY THE DIFFERENTIAL IN EXPANSION BETWEEN SAID BODY AND SAID WEAR RESISTANT INSERT AT OPERATING TEMPERATURES OF SAID PAPER MACHINE, SAID INSERT BEING FORMED OF A PLURALITY OF DISCRETE ELONGATED ELEMENTS GLUED TO A BACKING PLATE AND MAINTAINED IN END ABUTTING RELATIONSHIP.
 2. A drainage element as claimed in claim 1 wherein said wear resistant insert comprises a plurality of discrete elongated elements each having a wear resistant upper surface, flat end faces and beveled side edges; said elements being secured in end abutting relationship to a backing plate.
 3. A drainage element as claimed in claim 2 wherein said discrete elongated elements have a chamfered portion on their lower end faces and are glued to said backing plate while said elements are compressed in said end abutting relationship and glued onto said backing plate.
 4. A drainage element as claimed in claim 2 wherein said discrete elongated elements are compressed and glued together at their end faces and also glued to said backing plate with said plate in a stressed state.
 5. A drainage element as claimed in claim 2 wherein said backing plate is expanded by heat at a higher temperature than said insert elements, said elements being glued to said expanded backing plate in intimate end abutting reLationship with each other so that when the temperature of said backing plate is lowered the backing plate contracts applying compression stress to the elements in end abutment.
 6. An element as claimed in claim 2 wherein said undercut portion extends in the upper portion of said side wall, said beveled side edges of said elements being retained in said upper portion of said groove with said backing plate thereunder.
 7. An element as claimed in claim 1 wherein said wear resistant insert has a lower coefficient of thermal expansion than the coefficient of thermal expansion of said body. 